Various principles are known for recording information by irradiating a thin film (recording film) with an energy beam such as a laser. Among these, one principle utilizes the change in the atomic matrix that occurs from irradiating a laser onto a film material to induce a phase change (also called phase transition, phase change state), etc.
Usually an information recording medium is made up of a first protective layer, a recording film such as of Ge—Sb—Te alloy, an upper protective layer, and a reflective layer; and recording is performed by irradiating light to making the recording film amorphous, and erase performed by irradiating light to crystallize the film. The minimum mark size was determined by the diffraction limit of the spot.
Methods for reading (reproducing) marks below the diffraction limit that are known up to now are methods that utilized super resolution or magnifying the magnetic domain. Examples of this technology were disclosed in JP-A No. 269627/1998 for using the heat of a laser to read tiny marks by forming small optical apertures smaller than the spot size and utilizing a film such as Ge—Sb—Te as the super-resolution read layer. Another method called the MAMMOS (Magnetic amplifying magneto-optical system) as disclosed in JP-A No. 295479/1994 and JP-A No. 087041/2004, are known that form recording magnetic domains on an enlarged read (reproduction) layer by magnetic transcription, to fully enlarge the spot size of the read light by means of read light irradiated onto the recording magnetic domain from the read light irradiating section.